Method and apparatus for increasing a lifespan of nanopore-based dna sensing devices

ABSTRACT

Techniques for increasing the lifespan of a nanopore DNA sensing device are disclosed. A related DNA sensing device may be formed by a process comprising forming a first electrode, forming a second electrode, disposing the first electrode and second electrode within an insulator, and disposing a lipid bilayer having a nanopore between the first electrode and second electrode. The forming of the second electrode may comprise forming a silver (Ag) layer, pressing a mold into the Ag layer to form a pattern in the Ag layer, removing the mold from the Ag layer, and exposing the Ag layer to an electrolyte.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application for patent is a continuation of U.S. applicationSer. No. 15/587,373, entitled “Method and Apparatus For Increasing aLifespan of Nanopore-based DNA Sensing Devices”, filed May 4, 2017,which claims the benefit of U.S. Provisional Application No. 62/332,670,entitled “Method and Apparatus For Increasing a Lifespan ofNanopore-based DNA Sensing Devices”, filed May 6, 2016, assigned to theassignee hereof, and expressly incorporated herein by reference in itsentirety, assigned to the assignee hereof, and expressly incorporatedherein by reference in its entirety.

INTRODUCTION

Aspects of this disclosure relate generally to sensing devices fordeoxyribonucleic acid (DNA), and more particularly to methods andapparatuses for increasing the lifetime of nanopore-based DNA sensingdevices.

DNA, sometimes referred to as the “blueprint of life”, is a moleculethat stores biological information. The structure of DNA, famouslydiscovered by James Watson and Francis Crick, consists of two strands ofbiopolymer, coiled around one another to form a double helix. Eachstrand is a polynucleotide that includes a plurality of nucleotides, forexample, cytosine (“C”), guanine (“G”), adenine (“A”), and thymine(“T”). Each nucleotide in a first strand of DNA may be bonded to apaired nucleotide in the second strand, thereby forming a base pair.Generally, cytosine and guanine are paired to form a “G-C” or “C-G” basepair, and adenine and thymine are paired to form an “A-T” or “T-A” basepair.

Although the structure of DNA is now known, new methods for analyzingindividual DNA molecules are still being developed. Generally, theanalysis includes ‘reading’ the nucleotide sequence of a particular DNAstrand. In one method, known as nanopore DNA sequencing, a nanopore isimmersed in a conductive fluid, and a voltage is applied across thenanopore. As a result, ions are conducted through the nanopore, therebygenerating a measurable electric current. A DNA strand is thentransmitted through the nanopore, one nucleotide at a time. The presenceof a nucleotide within the nanopore disrupts the conduction of the ions,thereby causing a change in the electric current. Moreover, the changein electrical current due to a particular nucleotide differs from thechange in electrical current due to other nucleotides. Accordingly, anentire DNA strand can be transmitted through the nanopore and eachnucleotide in the strand can be identified based on the change incurrent.

As nanopore DNA sequencing improves, new challenges are presented. Forexample, the electrodes used to draw ions through the nanopore may wearout due to chemical changes. As a result, new technologies are neededfor increasing the lifespan of nanopore DNA sensing devices.

SUMMARY

The following summary is an overview provided solely to aid in thedescription of various aspects of the disclosure and is provided solelyfor illustration of the aspects and not limitation thereof.

In one example, a method of forming a DNA sensing device is disclosed.The method may include, for example, forming a first electrode, forminga second electrode, wherein forming the second electrode comprisesforming a silver (Ag) layer, pressing a mold into the Ag layer to form apattern in the Ag layer, removing the mold from the Ag layer, andexposing the Ag layer to an electrolyte, disposing the first electrodeand second electrode within an insulator, disposing a lipid bilayerhaving a nanopore between the first electrode and second electrode.

In another example, a method of forming an electrode is disclosed. Themethod may include, for example, forming a silver (Ag) layer, pressing amold into the Ag layer to form a pattern in the Ag layer, removing themold from the Ag layer, and exposing the Ag layer to an electrolyte.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are presented to aid in the description ofvarious aspects of the disclosure and are provided solely forillustration of the aspects and not limitation thereof.

FIG. 1 generally illustrates a nanopore DNA sensing device in accordancewith an aspect of the disclosure.

FIG. 2 generally illustrates a detail of a nanopore in accordance withan aspect of the disclosure.

FIG. 3A depicts a topographic view of a conventional electrode.

FIG. 3B depicts a tilted view of the conventional electrode of FIG. 3A.

FIG. 4 generally illustrates a method for fabricating an electrode inaccordance with an aspect of the disclosure.

FIG. 5A generally illustrates an electrode fabricated in accordance withthe method of FIG. 4 in a first stage of fabrication.

FIG. 5B generally illustrates an electrode fabricated in accordance withthe method of FIG. 4 in a second stage of fabrication.

FIG. 5C generally illustrates an electrode fabricated in accordance withthe method of FIG. 4 in a third stage of fabrication.

FIG. 5D generally illustrates an electrode fabricated in accordance withthe method of FIG. 4 in a fourth stage of fabrication.

FIG. 6A generally illustrates an electrode in accordance with an aspectof the disclosure from a topographic view.

FIG. 6B generally illustrates the electrode of FIG. 6A from across-sectional view.

FIG. 6C generally illustrates the electrode of FIG. 6A from a tiltedcross-sectional view.

FIG. 7A generally illustrates another electrode in accordance with anaspect of the disclosure from a topographic view.

FIG. 7B generally illustrates the electrode of FIG. 7A from across-sectional view.

FIG. 7C generally illustrates the electrode of FIG. 7A from a tiltedview.

FIG. 8A generally illustrates yet another electrode in accordance withan aspect of the disclosure from a topographic view.

FIG. 8B generally illustrates the electrode of FIG. 8A from a tiltedview.

DETAILED DESCRIPTION

The present disclosure relates generally to a method and apparatus forincreasing the lifespan of a nanopore DNA sensing device.

More specific aspects of the disclosure are provided in the followingdescription and related drawings directed to various examples providedfor illustration purposes. Alternate aspects may be devised withoutdeparting from the scope of the disclosure. Additionally, well-knownaspects of the disclosure may not be described in detail or may beomitted so as not to obscure more relevant details.

Those of skill in the art will appreciate that the information andsignals described below may be represented using any of a variety ofdifferent technologies and techniques. For example, data, instructions,commands, information, signals, bits, symbols, and chips that may bereferenced throughout the description below may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof, depending inpart on the particular application, in part on the desired design, inpart on the corresponding technology, etc.

Further, many aspects are described in terms of sequences of actions tobe performed by, for example, elements of a computing device. It will berecognized that various actions described herein can be performed byspecific circuits (e.g., Application Specific Integrated Circuits(ASICs)), by program instructions being executed by one or moreprocessors, or by a combination of both. In addition, for each of theaspects described herein, the corresponding form of any such aspect maybe implemented as, for example, “logic configured to” perform thedescribed action.

FIG. 1 generally illustrates a nanopore DNA sensing device 100 inaccordance with an aspect of the disclosure.

The nanopore DNA sensing device 100 includes a semiconductor device 110having a first semiconductor contact area 112 and a second semiconductorcontact area 114. As an example, the semiconductor device 110 mayinclude p-doped silicon and the semiconductor contact areas 112 and 114may include n-doped silicon and p-doped silicon. However, it will beunderstood that any suitable material may be selected. The nanopore DNAsensing device 100 may further include a conductor 116. The conductor116 may be used to apply a voltage V between the first semiconductorcontact area 112 and the second semiconductor contact area 114. In thearrangement of FIG. 1, the first semiconductor contact area 112constitutes a trans-electrode and the second semiconductor contact area114 constitutes a cis-electrode, but it will be understood that thepolarity of the voltage V may be reversed. Moreover, an electricalcurrent i through the conductor 116 may be, for example, detected,amplified, and/or measured. The changes in the current i may be used todetermine a DNA sequence, as will be discussed in greater detail below.

The nanopore DNA sensing device 100 further includes an insulator 120.The insulator 120 may include a first via 122 and a second via 124 incontact with the first semiconductor contact area 112 and the secondsemiconductor contact area 114, respectively. As an example, theinsulator 120 may include silicon dioxide (SiO2), however, it will beunderstood that any suitable material may be selected. The first via 122and the second via 124 may include, for example, tungsten (W), however,it will be understood that any suitable material may be selected.

The insulator 120 further includes a first electrode 130 and a secondelectrode 140 in contact with the first via 122 and the second via 124,respectively. The first electrode 130 may include an adhesion/diffusionlayer 134, a conductive layer 136, and a surface layer 138. Similarly,the second electrode 140 may include an adhesion/diffusion layer 144, aconductive layer 146, and a surface layer 148.

As an example, the adhesion/diffusion layer 134 may include a chromium(Cr) adhesion layer in contact with the first via 122 and a gold (Au)diffusion layer between the conductive layer 136 and the Cr adhesionlayer. Additionally or alternatively, the adhesion/diffusion layer 134may include titanium nitride (TiN). It will be understood that any othersuitable material may be selected to fabricate the adhesion/diffusionlayer 134. Like the adhesion/diffusion layer 134, the adhesion/diffusionlayer 144 may include Cr, Au, TiN, any other suitable material, or anycombination thereof.

The conductive layer 136 may include silver (Ag), however, it will beunderstood that any suitable material may be selected. Moreover, thesurface layer 138 may include silver chloride (AgCl), however, it willbe understood that any suitable material may be selected. Like theconductive layer 136 and surface layer 138, the conductive layer 146 andsurface layer 148 may include Ag, AgCl, any other suitable material, orany combination thereof.

The nanopore DNA sensing device 100 further includes a separation layer150 having a nanopore 152 embedded therein. As an example, theseparation layer 150 may include silicon nitride (Si3N4) and/or a lipidbilayer. However, it will be understood that any suitable material maybe selected.

The nanopore DNA sensing device 100 further includes a chamber 160. Thechamber 160 may hold a conductive fluid therein. The conductive fluidmay include, for example, one or more electrolytes, for example,chlorine electrolyte (Cl−), potassium electrolyte (K+), hydrogenelectrolyte (H+), or any other suitable material. The conductive fluidwithin the chamber 160 may be divided by the separation layer 150 into afirst subchamber 163 and a second subchamber 164. Fluid in the firstsubchamber 163 may be in contact with the surface layer 138 of theelectrode 130, and fluid in the second subchamber 164 may be in contactwith the surface layer 148 of the electrode 140. In the nanopore DNAsensing device 100 of FIG. 1, the first subchamber 163 may be a positivechamber (i.e., associated with a trans-electrode) and the secondsubchamber 164 may be a negative chamber (i.e., associated with acis-electrode), but it will be understood that the polarity of thechambers may be reversed.

FIG. 2 generally illustrates a detail of the nanopore 152 of FIG. 1 inaccordance with an aspect of the disclosure. As noted above, thenanopore 152 may be embedded in the separation layer 150, and theseparation layer 150 may separate the first subchamber 163 from thesecond subchamber 164. As noted previously, the separation layer 150 mayinclude a lipid bilayer.

The nanopore 152 may include, for example, a translocator 154 and anassembler 156. The translocator 154 permits passage of conductive fluidbetween the first subchamber 163 and the second subchamber 164. Forexample, if the second subchamber 164 is negatively charged and thefirst subchamber 163 is positively charged, then negative ions (forexample, Cl−) may pass from the second subchamber 164 to the firstsubchamber 163 via the translocator 154. In some implementations, thetranslocator 154 may include alpha hemolysin.

The assembler 156 may separate a double-stranded DNA molecule 200 into afirst DNA strand 201 and a second DNA strand 202 and/or combine thefirst DNA strand 201 and the second DNA strand 202 into thedouble-stranded DNA molecule 200. In some implementations, the assembler156 may include DNA polymerase.

FIG. 2 may illustrate either separation or combination of thedouble-stranded DNA molecule 200. For example, the double-stranded DNAmolecule 200 may move from the second subchamber 164 into the assembler156, where it is separated by the assembler 156 into the first DNAstrand 201 and the second DNA strand 202. The first DNA strand 201 maybe led into the translocator 154 and translocated across the separationlayer 150, from the second subchamber 164 to the first subchamber 163.As another example, the first DNA strand 201 may be drawn from the firstsubchamber 163 through the translocator 154 and into the assembler 156,where it is combined with the second DNA strand 202 into thedouble-stranded DNA molecule 200. The double-stranded DNA molecule 200may then be moved into the second subchamber 164.

In some implementations, the following method may be used to perform DNAsequencing using the nanopore DNA sensing device 100 of FIG. 1 and thenanopore 152 of FIG. 2. First, a voltage may be applied to the firstsemiconductor contact area 112 and the second semiconductor contact area114 via the conductor 116. As a result, a positive charge appears on thefirst electrode 130 and a negative charge appears on the secondelectrode 140.

As an example, the second electrode 140 may include a surface layer 148including AgCl and a conductive layer 146 including Ag. When the voltageV is applied (such that the second electrode 140 is negatively charged),the AgCl in the second electrode 140 may be converted into Ag andchlorine electrolytes, i.e., AgCl(s)+e−→Ag(s)+Cl−. As the secondelectrode 140 generates Cl− ions, the second subchamber 164 may becomenegatively charged.

Moreover, the first electrode 130 may include a surface layer 138including AgCl and a conductive layer 136 including Ag. When the voltageV is applied (such that the first electrode 130 is positively charged),the Ag in the first electrode 130 may combine with Cl− ions in the firstsubchamber 163, i.e., Ag(s)+Cl−→AgCl(s)+e−. As the first electrode 130combines Cl− ions into AgCl, the first subchamber 163 may becomepositively charged.

As a result, ions in the chamber 160 may have a tendency to flow towardeither the first subchamber 163 (which is positively charged) or thesecond subchamber 164 (which is negatively charged). For example, Cl−ions in the chamber 160 (including Cl− ions generated at the secondelectrode 140) may have a tendency to flow toward the positively-chargedfirst subchamber 163.

Moreover, as the first electrode generates electrons e− and the secondelectrode 140 absorbs electrons e−, the electrical current i flowingthrough the conductor 116 may also increase.

Because Cl− ions may have a tendency to flow toward thepositively-charged first subchamber 163, the Cl− ions may translocateacross the separation layer 150 via the nanopore 152. However, thenanopore 152 may also be configured to translocate DNA (for example, thefirst DNA strand 201, as shown in FIG. 2).

As the first DNA strand 201 shown in FIG. 2 is being translocated, itmay impede the flow of Cl− ions through the nanopore 152. As a result,the current i may be reduced due to the translocation of the first DNAstrand 201. Moreover, different types of nucleotide may have differenteffects on the flow of Cl− ions through the nanopore 152.

Accordingly, as different types of nucleotide pass through the nanopore152, different quantities of Cl− ions may pass through the nanopore 152,and a different electrical current i may be measured on the conductor116. For example, a C nucleotide may cause a current iC, an A nucleotidemay cause a current iA, a T nucleotide may cause a current iT, and a Gnucleotide may cause a small current iG. As the first DNA strand 201passes through the nanopore 152, the nanopore DNA sensing device 100will generate a current waveform i(t) that indicates the sequence ofnucleotides in the first DNA strand 201.

FIGS. 3A-3B generally illustrate portions of a conventional electrode300. FIG. 3A depicts a topographic view of the electrode 300, whereasFIG. 3B depicts a tilted view of the electrode 300. The electrode 300may include a surface layer 338 and a conductive layer 336. The surfacelayer 338 and the conductive layer 336 may be analogous to the surfacelayer 138 and the conductive layer 136, respectively, depicted inFIG. 1. The electrode 300 may have a length 310 and a width 320.

If the electrode 300 is included in the nanopore DNA sensing device 100,then it will be disposed on the insulator 120 such that the surfacelayer 338 is in contact with the chamber 160. The footprint of theelectrode 300 may be substantially equal to the length 310 multiplied bythe width 320. For example, if the length 310 has a value of L and thewidth 320 has a value of W, then the footprint of the electrode 300 maybe equal to LW.

Similarly, the surface layer 338 of the conventional electrode 300 mayhave a surface area that is substantially equal to the length 310multiplied by the width 320. For example, if the length 310 has a valueof L and the width 320 has a value of W, then the surface area of thesurface layer 338 may be equal to LW. It will be understood that if theelectrode 300 is included in the nanopore DNA sensing device 100, thenthe surface area of the surface layer 338 will be substantially equal tothe footprint of the electrode 300.

The lifespan of the nanopore DNA sensing device 100 may be limited basedon the surface area LW of the electrode 300. For example, in theconventional electrode 300, the surface layer 338 may be made of AgCland the conductive layer 336 may be made of Ag. If the electrode 300 isused as a trans-electrode, then the nanopore DNA sensing device 100 maylose sensitivity as the conductive layer 336 absorbs ions. Inparticular, over the lifespan of the nanopore DNA sensing device 100,the volume of AgCl may increase as Cl− ions are absorbed from thechamber 160 and combined with the Ag. Because the volume of AgClincreases at the expense of the volume of Ag, the nanopore DNA sensingdevice 100 may lose effectiveness (for example, reduced sensitivity,etc.).

However, as will be discussed in greater detail below, if the surfacearea of the surface layer can be increased, then the lifespan of thenanopore DNA sensing device 100 may also be increased. Moreover, if thesurface area of the surface layer can be increased without alsoincreasing the size of the footprint of the electrode, then the lifespanof the nanopore DNA sensing device 100 can be increased withoutincreasing the overall size of the nanopore DNA sensing device 100.

FIG. 4 generally illustrates a method 400 for fabricating an electrodein accordance with an aspect of the disclosure. The electrode may beincluded, for example, in the nanopore DNA sensing device 100 of FIG. 1.As will be appreciated for the following discussion, in an electrodefabricated in accordance with the method 400, the size of the surfacearea of the surface layer may be greater than the footprint of theelectrode.

At 410, a conductive layer is provided. The conductive layer may beanalogous to, for example, the conductive layer 136 and/or theconductive layer 146 depicted in FIG. 1. The conductive layer may have alength in a length direction and a width in a width direction. Theconductive layer may be substantially uniform in a depth direction. Forexample, the conductive layer may be flat, for example, formed as aplanar surface. The conductive layer may include, for example, Ag. Thelayer provided at 410 may be formed via electroplating or physical vapordeposition (PVD).

At 420, a patterned mold is provided. The patterned mold may include apatterned portion have a three-dimensional pattern. For example, thepatterned portion of the patterned mold may have a length, a width, anda depth. In some implementations, the width of the patterned portion maybe substantially equal to the width of the conductive layer and a lengthof the patterned portion may be substantially equal to the length of theconductive layer provided at 410. The patterned mold may besubstantially non-uniform in a depth direction, for example, formed as anon-planar surface. The patterned mold may include, for example, apolymer or any other suitable material.

At 430, the conductive layer provided at 410 is optionally softened. Thesoftening at 430 may be performed by, for example, heating theconductive layer. If the conductive layer includes Ag, then thesoftening at 430 may include heating the conductive layer to atemperature of between one-hundred-fifty degrees Celsius andfour-hundred degrees Celsius.

At 440, the patterned mold provided at 420 is pressed into theconductive layer provided at 410. The pressing at 440 may causedeformation of the conductive layer. If the conductive layer is softenedat 430, then the pressing at 440 may be performed while the conductivelayer is in a softened state. The patterned mold may be aligned with theconductive layer such that the width direction of the patterned mold andthe width direction of the conductive layer are substantially parallel.Moreover, the patterned mold may be aligned with the conductive layersuch that the length direction of the patterned mold and the lengthdirection of the conductive layer are substantially parallel. Moreover,the patterned mold may be pressed, at least in part, in the depthdirection of the patterned mold.

At 450, the conductive layer provided at 410 is optionally hardened. Thehardening at 450 may be performed by, for example, cooling theconductive layer. If the conductive layer includes Ag, then thehardening at 450 may include cooling the conductive layer to below onehundred and fifty degrees Celsius.

At 460, the patterned mold is removed from the conductive layer. If theconductive layer is hardened at 450, then the removing at 460 may beperformed while the conductive layer is in a hardened state. After theremoving at 460, the conductive layer may have a molded surface thattakes the opposite shape of the mold, for example, formed as anon-planar molded surface. In particular, the molded surface of theconductive layer may be substantially non-uniform in the depthdirection.

At 470, a molded surface of the conductive layer is exposed to anelectrolyte. The exposing at 470 may result in the forming of a surfacelayer analogous to, for example, the surface layer 138 and/or thesurface layer 148 depicted in FIG. 1. The surface layer may besubstantially non-uniform in the depth direction. The electrolyte maybe, for example, Cl−.

FIGS. 5A-5D generally illustrate, in various stages of fabrication, anelectrode 500 fabricated in accordance with the method 400 of FIG. 4.

FIG. 5A generally illustrates an electrode 500 fabricated in accordancewith the method of 400 prior to the pressing at 440. FIG. 5A depicts aninsulator 520 (analogous to, for example, the insulator 120 depicted inFIG. 1), a via 522 (analogous to, for example, the via 122 and/or thevia 124 depicted in FIG. 1), an adhesion/diffusion layer 534 (analogousto, for example, the adhesion/diffusion layer 134 and/or theadhesion/diffusion layer 144 depicted in FIG. 1), and a conductive layer536 (analogous to, for example, the conductive layer 136 and/or theconductive layer 146 depicted in FIG. 1). The electrode 500 may have afootprint 501. Although only one dimension of the two-dimensionalfootprint 501 is shown in FIG. 5A, it will be understood that thefootprint 501 may have a length L as well as width W. Moreover, it willbe understood from FIG. 5A that the size of the footprint 501 issubstantially equal to the surface area of the conductive layer 536(LW).

FIG. 5A further depicts a patterned mold 590 having a patterned portionthat is substantially non-uniform in a depth direction 592. Afterproviding the conductive layer 536 and the patterned mold 590 (as at 410and 420 in FIG. 4), the conductive layer 536 may be optionally softened(as at 430 in FIG. 4). FIG. 5A further depicts a depth direction 592 inwhich the patterned mold 590 may be pressed (as at 440 in FIG. 4).

FIG. 5B generally illustrates an electrode 500 fabricated in accordancewith the method of 400 after the pressing of the patterned mold 590 intothe conductive layer 536 (as at 440 in FIG. 4). Accordingly, a patternedportion of the patterned mold 590 is in contact with the conductivelayer 536. Because the patterned portion of the patterned mold 590 issubstantially non-uniform in a depth direction, pressing of thepatterned mold 590 against the conductive layer 536 causes theconductive layer 536 to take the opposite shape of the patterned portionof the patterned mold 590. After pressing the conductive layer 536 (asat 440 in FIG. 4), the conductive layer 536 may be optionally hardened(as at 450 in FIG. 4).

FIG. 5C generally illustrates an electrode 500 fabricated in accordancewith the method of 400 after the removing of the patterned mold 590 fromthe conductive layer 536 (as at 460 in FIG. 4). As can be understoodfrom FIG. 5C, the conductive layer 536 may maintain the opposite shapeof the patterned portion of the patterned mold 590, even after thepatterned mold 590 is removed. In particular, the conductive layer 536may be substantially non-uniform in the depth direction.

FIG. 5D generally illustrates an electrode 500 fabricated in accordancewith the method of 400 after the exposing of the conductive layer 536 toan electrolyte 594 (as at 470 in FIG. 4). The electrolyte 594 may causea surface layer 538 to form on a surface of the conductive layer 536.For example, if the conductive layer 536 include Ag and the electrolyte594 includes Cl−, then the surface layer 538 depicted in FIG. 5D mayinclude AgCl.

Although only one dimension of the two-dimensional footprint 501 isshown in FIG. 5D, it will be understood that the size of the footprint501 as depicted in FIG. 5D is substantially equal to the size of thefootprint 501 as depicted in FIG. 5A (LW). However, it will be furtherunderstood that the surface area of the surface layer 538 has increased,and is now greater than the size of the footprint 501. This is due tothe fact that the surface layer 538 is substantially non-uniform in thedepth direction.

FIGS. 6A-6C generally illustrate an electrode 600 fabricated inaccordance with the method of 400. FIG. 6A generally illustrates theelectrode 600 from a topographic view. FIG. 6B generally illustrates theelectrode 600 from a cross-sectional view. FIG. 6C generally illustratesthe electrode 600 from a tilted cross-sectional view.

The electrode 600 includes a conductive layer 636 and a surface layer638. The size of the footprint of the electrode 600 is defined as anelectrode length 601 of the electrode 600 multiplied by an electrodewidth 602 of the electrode 600.

The electrode 600 further includes one or more fins 610 and one or moretrenches 620. Each fin 610 and each trench 620 may have a length that isequal to the electrode length 601. However, as can be seen from FIG. 6A,the fin width 612 may be less than the electrode width 602. Moreover,the trough width 622 may be less than the electrode width 602.

Each fin 610 may also have a fin depth 613. The fin depth 613 may beequal to a distance in a depth direction between a top surface of thefin 610 and a top surface of an adjacent trench 620.

As can be understood from FIGS. 6A-6C, the surface area of the surfacelayer 638 exceeds the size of the footprint of the electrode 600. As anexample, consider a scenario wherein the electrode 600 has an electrodelength 601 equal to ten micrometers (10 μm) and an electrode width 602equal to 10 μm. In this scenario, the footprint of the electrode 600will be equal to one hundred square micrometers (100 μm2). If thesurface layer 638 were uniform in a depth direction, then the surfacearea of the surface layer 638 would also be equal to 100 μm2. However,because the surface layer 638 is non-uniform in a depth direction, thesurface area of the surface layer 638 will be greater than 100 μm2. Forexample, given a fin width 612 of 2 μm, a trough width 622 of 2 μm, anda fin depth 613 of 3 μm, the surface area of the surface layer 638 maybe approximately 220 μm2.

FIGS. 7A-7C generally illustrate another electrode 700 fabricated inaccordance with the method of 400. FIG. 7A generally illustrates theelectrode 700 from a topographic view. FIG. 7B generally illustrates theelectrode 700 from a cross-sectional view. FIG. 7C generally illustratesthe electrode 700 from a tilted view.

The electrode 700 includes a conductive layer 736 and a surface layer738. The size of the footprint of the electrode 700 is defined as anelectrode length 701 of the electrode 700 multiplied by an electrodewidth 702 of the electrode 700.

The electrode 700 further includes one or more pillars 710 and a basesurface 720. Each pillar 710 may have a pillar length 711 and a pillarwidth 712. However, as can be seen from FIG. 7A, the pillar length 711may be less than the electrode length 701 and the pillar width 712 maybe less than the electrode width 702. A pillar 710 may be displaced froman adjacent pillar 710 by a pillar spacing distance 721.

Each pillar 710 may also have a pillar depth 713. The pillar depth 713may be equal to a distance in a depth direction from a top surface of apillar 710 to a top surface of the base surface 720.

As can be understood from FIGS. 7A-7C, the surface area of the surfacelayer 738 exceeds the size of the footprint of the electrode 700. As anexample, consider a scenario wherein the electrode 700 has an electrodelength 701 equal to 10 μm and an electrode width 702 equal to 10 μm. Inthis scenario, the footprint of the electrode 700 will be equal to onehundred square micrometers (100 μm2). If the surface layer 738 wereuniform in a depth direction, then the surface area of the surface layer738 would also be equal to 100 μm2. However, because the surface layer738 is non-uniform in a depth direction, the surface area of the surfacelayer 738 will be greater than 100 μm2. For example, given a pillarlength 711, pillar width 712, and pillar spacing distance 721 equal to 2μm, and a pillar depth 713 equal to 3 μm, the surface area of thesurface layer 738 will be approximately 240 μm2.

FIGS. 8A-8B generally illustrate yet another electrode 800 fabricated inaccordance with the method of 400. FIG. 8A generally illustrates theelectrode 800 from a topographic view. FIG. 8B generally illustrates theelectrode 800 from a tilted view.

The electrode 800 includes a number of components that are analogous tothe conductive layer 736, surface layer 738, pillars 710 and basesurface 720 depicted in FIGS. 7A-7C. Accordingly, only the differenceswill be described here.

Unlike the pillars 710, electrode 800 includes at least one hollowpillar having a hollow 810. The hollows may have a hollow length 811that is smaller than the pillar length 711 and a hollow width 812 thatis smaller than the pillar width 712. In some implementations, thehollow depth of each hollow 810 may be equal to the pillar depth 713. Ascan be understood from FIGS. 8A-8B, the surface area of the surfacelayer 838 exceeds the size of the footprint of the electrode 800, andfurther exceed the surface area of the surface layer 738 of theelectrode 700 depicted in FIG. 7.

While the foregoing disclosure shows various illustrative aspects, itshould be noted that various changes and modifications may be made tothe illustrated examples without departing from the scope defined by theappended claims. The present disclosure is not intended to be limited tothe specifically illustrated examples alone. For example, unlessotherwise noted, the functions, steps, and/or actions of the methodclaims in accordance with the aspects of the disclosure described hereinneed not be performed in any particular order. Furthermore, althoughcertain aspects may be described or claimed in the singular, the pluralis contemplated unless limitation to the singular is explicitly stated.

What is claimed is:
 1. A deoxyribonucleic acid (DNA) sensing deviceformed by a process, the process comprising: forming a first electrode;forming a second electrode, wherein forming the second electrodecomprises: forming a silver (Ag) layer; pressing a mold into the Aglayer to form a pattern in the Ag layer; removing the mold from the Aglayer; and exposing the Ag layer to an electrolyte; disposing the firstelectrode and the second electrode within an insulator; disposing alipid bilayer having a nanopore between the first electrode and thesecond electrode.
 2. The DNA sensing device of claim 1, wherein theforming of the Ag layer comprises electroplating or physical vapordeposition (PVD).
 3. The DNA sensing device of claim 1, wherein theforming of the Ag layer comprises forming the Ag layer on a diffusionlayer and an adhesion layer comprising: gold (Au) and chromium (Cr);titanium nitride (TiN); or any combination thereof.
 4. The DNA sensingdevice of claim 1, further comprising: heating the Ag layer to atemperature of between one-hundred-fifty and four-hundred degreesCelsius prior to the pressing of the mold; and cooling the Ag layerafter the pressing of the mold.
 5. The DNA sensing device of claim 1,wherein the mold is a polymer mold configured to form the pattern in theAg layer.
 6. The DNA sensing device of claim 1, wherein: the forming ofthe Ag layer comprises forming an Ag layer with at least one planarsurface; and the forming of the pattern in the Ag layer comprisesdeformation of the at least one planar surface into at least onenon-planar surface, wherein a surface area of the at least onenon-planar surface is greater than a surface area of the at least oneplanar surface.
 7. The DNA sensing device of claim 6, wherein thepattern is a trench.
 8. The DNA sensing device of claim 6, wherein thepattern is a pillar.
 9. The DNA sensing device of claim 6, wherein thepattern is a hollow pillar.
 10. The DNA sensing device of claim 1,wherein the electrolyte is a chlorine electrolyte (Cl⁻), and theexposing forms a silver chloride (AgCl) layer.
 11. An electrode formedby a process, the process comprising: forming a silver (Ag) layer;pressing a mold into the Ag layer to form a pattern in the Ag layer;removing the mold from the Ag layer; and exposing the Ag layer to anelectrolyte.
 12. The electrode of claim 11, wherein the forming of theAg layer comprises electroplating or physical vapor deposition (PVD).13. The electrode of claim 11, wherein the forming of the Ag layercomprises forming the Ag layer on a diffusion layer and an adhesionlayer comprising: gold (Au) and chromium (Cr); titanium nitride (TiN);or any combination thereof.
 14. The electrode of claim 11, furthercomprising: heating the Ag layer to a temperature of betweenone-hundred-fifty and four-hundred degrees Celsius prior to the pressingof the mold; and cooling the Ag layer after the pressing of the mold.15. The electrode of claim 11, wherein the mold is a polymer moldconfigured to form the pattern in the Ag layer.
 16. The electrode ofclaim 11, wherein: the forming of the Ag layer comprises forming an Aglayer with at least one planar surface; and the forming of the patternin the Ag layer comprises deformation of the at least one planar surfaceinto at least one non-planar surface, wherein a surface area of the atleast one non-planar surface is greater than a surface area of the atleast one planar surface.
 17. The electrode of claim 16, wherein thepattern is a trench.
 18. The electrode of claim 16, wherein the patternis a pillar.
 19. The electrode of claim 16, wherein the pattern is ahollow pillar.
 20. The electrode of claim 11, wherein the electrolyte isa chlorine electrolyte (Cl⁻), and the exposing forms a silver chloride(AgCl) layer.